The general aim of this project is to study the molecular mechanisms of free energy transduction in biology, such as in muscle contraction, active transport, etc.. During this period, a number of different topics related to this project have been studied. The most important areas in which progress has been made are: (1) A theoretical model simulation study on the response of contracting muscles to multiple periodic perturbations in force and length. The results of the calculations are used to resolve the question of how many power-strokes (or rowing motions) an actomyosin crossbridge in a contracting muscle fiber can perform during one ATP hydrolysis cycle; (2) A theoretical model study of experimentally measured active transport of Rb+ ions across red blood cell membranes induced by a randomly fluctuating electric field. The parameters of a four-state carrier model that fits experimental data are obtained; (3) The study of diffusion and dequenching of self-quenching fluorophores in membranes of two fused cells. A simplified formula for the dequenching kinetics is obtained, which is useful in elucidating the mechanisms of the glycoprotein-mediated cell- cell fusion reaction.